(1) Field of the Invention
This invention relates to fiber optics and in particular to connectors for optical fibers in data communications systems.
(2) Description of the Prior Art
The concept of using optical fibers in data communications is now well established. See, for example, "Fiber Optic Developments Spark Worldwide Interest," R. Gundlach, Electronics, Aug. 5, 1976. Regardless of the desirable features of interference-free, large bandwidth communications which are envisioned, the commercial utilization of such data transmitting links has been impeded by the problems of making reliable, inexpensive and low-loss connection between fibers or between a given fiber and an associated optical element such as a light source or photodetector. Such connections must address at least three types of problems: axial alignment, longitudinal alignment or gap between associated members, and angular alignment.
Axial alignment is commonly achieved by use of precision sleeves which conform precisely to the outer diameter of the fiber, thereby guiding fibers inserted therein into axial position such that they may then be secured in place. U.S. Pat. Nos. 3,972,585, 4,005,522 and 4,008,948 (Dalgleish et al) depict various connectors employing sleeves into which exposed fiber ends are directly inserted.
Such connectors address the problem of longitudinal alignment or end gap by positioning the fiber ends to extend a predetermined distance such that when the respective ends are inserted from opposite ends of the sleeve, they meet at a predetermined position to abut or to be in very close end to end relationship (see Column 2, lines 39-41 of U.S. Pat. No. 3,972,585). Typical connectors require extensive time-consuming jigging operations to ensure proper positioning of the fiber ends, or utilize small gaps and index matching fluids to prevent scratching and damage to the fiber ends due to mutual contact.
In order to avoid such jigs and precise positioning of the fiber ends, techniques are also known for encasing an end of an optical fiber in a sleeve or other terminal member and of then polishing and/or grinding the joined end of the fiber and terminal member, causing both members to become coplanar and optically flat (see U.S. Pat. No. 3,861,781, Hasegawa et al, Column 2, lines 39-43). The polished fiber ends are then positioned by butting together the surrounding sleeves within a third close fitting shroud. Since the fiber ends are planar with the sleeves, such systems do not avoid problems associated with scratching or chipping of the fiber ends due to frictional contact.